Abstract Epilepsy is a severe neurological disease affecting more than 65 million people worldwide and is characterized by unpredictable abnormal electrical discharges resulting in recurrent seizures. About one third of patients with epilepsy suffer from intractable seizures that do not respond to anti-seizure medications (ASMs). Neurosurgical interventions and neurostimulator devices are useful options for only a fraction of patients with drug-refractory seizures, underscoring the urgent need to develop new therapies. One strategy with considerable promise is to engraft new neurons to provide enhanced GABAergic inhibition in an activity-dependent manner. However, use of fetal neurons for cell therapy is associated with practical and ethical issues. Therefore, to overcome such hurdles, in our previous studies, we pioneered the transplantation of human pluripotent stem cell (hPSC)-derived medial ganglionic eminence (MGE)-type human cortical interneurons (cINs) into epileptic mouse brains and demonstrated their integration into dysfunctional circuitry, accompanied by the suppression of seizures and comorbid behavioral abnormalities. Furthermore, more recently, we have determined the optimal stage of human cIN differentiation to ensure maximal integration into host circuitry as well as safety without risk of tumor formation, and developed a method to efficiently generate these safe and highly migratory populations of synchronized early postmitotic cINs from hPSCs in large quantities, bringing cell therapy for epilepsy one step closer to reality. Furthermore, we have successfully tested the efficacy of human early postmitotic cINs in 2 different models of temporal lobe epilepsy (TLE), observing >80% of seizure reduction. With these strong previous studies, now we are ready to embark clinical translation of this novel and restorative therapy for epilepsy patients with limited options. Thus, in this proposed study, we will scale up production of synchronized early postmitotic cINs that are optimal for grafting under cGMP condition. For added safety, we will utilize well- characterized HLA-edited hypoimmunogenic iPSCs to minimize the need for immunosuppression for off-the- shelf use of human cINs. We will also extensively analyze the produced early postmitotic cINs’ phenotype, efficacy, safety, tumorigenesis and biodistribution to seek IND approval. Once we obtain IND approval, we will do a first-in-human clinical trial of early postmitotic cIN grafting with a primary goal of safety analysis, while also checking efficacy as a secondary measure. This will be done in patients with intractable TLE who are candidates for resection while they undergo intracranial EEG to identify the seizure focus without additional invasive steps. Completion of these studies is pivotal for translating this experimental therapy into a viable therapeutic strategy for intractable epilepsy.

Narrative Epilepsy, a debilitating neurological disorder characterized by unpredictable and abnormal electrical discharges and recurrent seizures, affects more than 65 million people worldwide, with one third of cases not being adequately controlled with existing therapies. In this study, we will carry out IND-enabling studies and the first-in- human clinical trials to move pluripotent stem cell-derived human cortical interneuron transplantation into clinical reality. This work will be pivotal in bringing this novel and restorative therapy to patients with epilepsy who have limited options.